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The Phetchaburi River (Thai: แม่น้ำเพชรบุรี, RTGS: Maenam Phetchaburi, pronounced [mɛ̂ːnáːm pʰét.t͡ɕʰā.bū.rīː]) is a river in western Thailand. It has its source in the Tenasserim Hills, in the Kaeng Krachan National Park, Kaeng Krachan district and flows through Tha Yang, Ban Lat, Mueang Phetchaburi and mouths into the Bay of Bangkok in Ban Laem district. It is 210 kilometres (130 mi) long, most of which is within the Phetchaburi Province. It is the backbone of this province.

The significance of the water in this river is that it has been used in the coronation ceremonies of each Thai king. As well, the point where the river flows through Tambon Tha Chai, Ban Lat district was used as a drink for Phra Sutharos (royal drinking water) during the Rama V's reign.^[1]

13°15′57″N 99°56′32″E / 13.2657°N 99.9423°E / 13.2657; 99.9423